1. Field of the Invention
The present invention relates to a passenger detecting device that is adapted for a motor vehicle and is capable of surely detecting information on a passenger on a seat thereof.
2. Description of the Related Art
A conventional passenger detecting device, adapted for motor vehicle, of this kind is disclosed in Japanese patent laid-open publication No. 2000-302003. This conventional passenger detecting device has a seat belt sensor for detecting whether a seat belt on a seat is fastened or not, and a seat sensor for detecting existence and weight of a passenger on the seat. When the seat belt sensor detects that the seat belt is fastened and the seat sensor detects existence of a passenger on a seat, the weight of the passenger is measured based on an output of the seat sensor. This detected weight data is stored and maintained to judge the passenger to be an adult, a little adult, or a child so that actuation of an air bag can be controlled, based on its judgment result, according to a physical size of the passenger, while the weight data is erased when the seat belt sensor detects unfastening of the seat belts.
The above known conventional passenger detecting device, however, encounters a problem in that information on the passenger on the seat can not be stably and properly obtained in some cases. For example, a child having heavy luggage may get in a motor vehicle and sit on the seat. In this case, when the child fastens the seat belt with the luggage, his or her weight is measured by the seat sensor and the passenger on the seat is judged to be an adult depending on the weight of the luggage. After this judgment, the child is not judged to be a child any longer by the conventional passenger detecting device even when he or she moves the luggage to another seat or another place. In another case, it may not properly detect the weight of a passenger when the passenger fastens a seat belt while a motor vehicle runs, especially, suddenly accelerates and is suddenly braked.
It is, therefore, an object of the present invention to provide a passenger detecting device adapted for motor vehicle which overcomes the foregoing drawbacks and can more stably and properly detect information on a passenger on a seat than the conventional passenger detecting devices.